1. Technical Field
The present invention relates to a position pointer of the electromagnetic induction type and an electronic ink cartridge accommodated in the position pointer of the electromagnetic induction type.
2. Description of the Related Art
A coordinate inputting apparatus of the electromagnetic induction type is configured from a position detection apparatus and a position pointer of a shape of a pen as disclosed, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2002-244806). The position detection apparatus includes a sensor configured from a large number of loop coils disposed in an X-axis direction and a Y-axis direction of coordinate axes. The position pointer has a resonance circuit configured from a coil as an example of an inductance element wound around a magnetic core and a capacitor.
The position detection apparatus supplies a transmission signal of a predetermined frequency to the loop coils of the sensor, and each loop coil transmits the transmission signal as electromagnetic energy to the position pointer. The resonance circuit of the position pointer is configured such that it has a resonance frequency corresponding to the frequency of the transmission signal and cooperates with a loop coil of the sensor to store the electromagnetic energy based on an electromagnetic induction action. Then, the position pointer returns the electromagnetic energy stored in the resonance circuit to the loop coil of the sensor of the position detection apparatus.
The loop coil of the sensor detects the electromagnetic energy from the position pointer. The position detection apparatus detects coordinate values in the X-axis direction and the Y-axis direction on the sensor pointed to by the position pointer from the position of the loop coil from which the transmission signal is supplied and the position of the loop coil which detects the electromagnetic energy from the resonance circuit of the position pointer.
The position pointer of the type described has a configuration which can detect a writing pressure by the position detection apparatus when force applied to a core member of the position pointer of a shape of a pen, namely, the writing pressure, is transmitted as a variation of the resonance frequency (or phase) of the resonance circuit to the position detection apparatus. As an example of the configuration which varies the resonance frequency of the resonance circuit in response to the writing pressure, a configuration which varies the inductance of the coil which configures the resonance circuit is known. The example of Patent Document 1 is an example of a position pointer which detects the writing pressure from the variation of the inductance.
FIG. 21 is a sectional view of a related-art position pointer 100 which detects the writing pressure from a variation of the inductance. As illustrated in FIG. 21, the position pointer 100 is configured such that a ferrite core 104 on which a coil 105 is wound and a ferrite chip 102 are opposed to each other with an O ring 103 interposed therebetween such that the ferrite chip 102 moves toward the ferrite core 104 when pressing pressure (writing pressure) is applied to a core member 101. The O ring 103 used here is a ring-shaped elastic member made of an elastic material such as synthetic resin or synthetic rubber and having a cross section of a shape of the alphabetical letter “O.”
In a case 111 of the position pointer 100, a printed board 114, a board holder 113, connecting wires 116 and a buffer member 117 are accommodated in addition to the parts described above. The printed board 114 has a plurality of resonant capacitors 115a to 115h disposed thereon, and the board holder 113 holds the printed board 114. The connecting wires 116 connect the coil 105 to the resonant capacitors 115a to 115h of the printed board 114 to configure a resonance circuit. The members accommodated in the case 111 are fixed at respective positions by a cap 112.
If the ferrite chip 102 against which the core member 101 configuring a pen tip abuts moves toward the ferrite core 104 in response to pressing force applied to the core member 101, then the inductance of the coil 105 wound on the ferrite core 104 varies in response to the movement of the ferrite chip 102. Thereupon, the phase (resonance frequency) of an electromagnetic induction signal transmitted from the coil 105 of the resonance circuit varies. The position detection apparatus can receive the variation of the phase (resonance frequency) of the electromagnetic induction signal from the position pointer by a loop coil thereby to detect the writing pressure applied to the core member of the position pointer.
Further, in the example of FIG. 21, the printed board 114 has a push switch 118 as a switch circuit provided thereon. The push switch 118 is switched on or off when a user presses a pressing portion thereof which is exposed to the outside of the case 111 through a through-hole (not illustrated) formed in a side wall of the case 111. The push switch 118 controls connection or disconnection of the capacitors 115e to 115h from among the resonant capacitors 115a to 115h to the resonance circuit. Accordingly, since the capacitance value of the capacitor connected in parallel in the resonance circuit is changed by switching the push switch 118 on or off, the phase (resonance frequency) of the electromagnetic induction signal transmitted from the coil of the resonance circuit to the position detection apparatus varies.
The position detection apparatus can detect an operation of the push switch 118 of the position pointer 100 by detecting the variation of the phase (frequency) of the electromagnetic induction signal from the position pointer 100 received by the loop coil. It is to be noted that the on/off operation of the push switch 118 detected by the position detection apparatus is allocated to various functions such as, for example, a determination (decision) operation input on an electronic apparatus such as a portable apparatus having the position detection apparatus built therein or a personal computer externally connected to the position detection apparatus.